RNA/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby. Tim is pouring protein powder into a blender. TIM: Protein. Gotta get your protein. A blender is heard. Moby is shown handing a letter to Tim. MOBY: Beep. TIM is heard reading from a typed letter. TIM: Dear Tim & Moby, I get that DNA holds the instructions for your cells; but how do the instructions get carried out? From, Olive. Good question, Olive! It sounds like you already know the basics. Almost every living cell contains DNA, or deoxyribonucleic acid. The screen is divided into four equal sections. In each section, an image shows a different type of cell. Organelles are shown within each cell. In one of the cells, an inset view appears and is radiating out from the nucleus. A strand of DNA is shown in the inset view. TIM: It's responsible for the differences between organisms. And it also controls how cells differ within an organism. Each cell is shown fading away as an ant, Tim, a duck and a plant appear in place of each of the four cells. MOBY: Beep? TIM: Think about it—cells are incredibly diverse. Motor nerves are long strings that transmit signals throughout your body. An electrical current is heard. An image shows a long, thin strand with cylindrical shapes threaded along it. One end of the figure resembles the branches on a tree. The other end of the figure is flat with eight tendril-like structures radiating out from the center. A starburst flashes as it moves from one end of the strand to the other. TIM: They're almost nothing like white blood cells, which are tiny spheres that help you fight infections. The screen divides vertically in two equal sections. An animation shows a sphere with small mushroom-like protrusions enter the screen. TIM: So what makes one a germ-killing machine, while the other acts like an electric wire? The sphere now has a face and is wearing boxing gloves. The sphere is punching the two gloves together. An electrical current is heard. A starburst flashes as it moves from one end of the strand to the other. MOBY: Beep? TIM: The difference lies in molecules called proteins, the building block of all cells. DNA tells your cells which proteins to make, when to make them, and what to do with them. It tells your lens cells to form out of clear proteins, so light can shine in. It tells cells in your pancreas to make insulin, which lets your body process sugar. The screen divides vertically into two equal sections. In one section, an animation shows a beam of light reflecting off a chess piece into a human eye. In the other section, an animation shows four shapes. Two of the shapes are green, one is orange and one is purple. A large group of variously colored small spheres are exiting the purple shape. TIM: All of these proteins are assembled right when they're needed, inside the cell. Moby: Beep? TIM: They're made out of simpler molecules called amino acids. The average human protein consists of hundreds of amino acids linked together. An animation shows a cluster of randomly organized different colored spheres. The spheres begin to separate from the cluster forming smaller groups in the shapes of different amino acids. Each group is labeled with the name of the amino acid that it represents. TIM: That's why protein is such an important part of the diet. Your body breaks it down into amino acids, the raw materials for … well, you. An animation shows Moby biting a raw steak. Blood surrounds Moby's mouth. TIM: So, assuming you eat right, your cells are swimming with amino acids. The screen divides vertically into two equal sections. In one section, an animation shows a steak. The screen rapidly zooms into the steak showing groups of floating spheres connected by small tubes. In the other section, an animation shows a cell. The screen rapidly zooms into the cell showing groups of floating spheres connected by small tubes organized into the shapes of amino acids within the cell. TIM: Structures called ribosomes stand ready to string them together into proteins. All they need are some instructions to follow. The section containing the cell enlarges to reveal more details of the cell. Three figures are glowing green. The figures resemble a thick star. MOBY: Beep? TIM: The protein "recipes" are encoded in DNA's unique structure. An animation of a cell rapidly zooms into the center of the cell. Inside the center, a figure resembling an Upper X is shown. The screen continues to zoom into the Upper X. Inside, an image shows a double helix. The double helix is zoomed in on until only a portion of it resembling an oblong circle is shown. Running from one side of the circle to the other side are six small tubes. Each tube is divided into two different colors. Some are half green half red while the others are half blue half yellow. TIM: It's kind of a spiral staircase shape called a double-helix. Each "step" is made up of a pair of molecules called bases. Each tube blinks one at a time. TIM: There are four different bases, and they stick together like puzzle pieces, always in the same pairs. An animation zooms in on two of the tubes. The tubes separate and reconnect at the point where their two colors intersect. MOBY: Beep? TIM: You can think of bases as the words in a special kind of language. Each set of three bases translates to a specific amino acid. These base triplets are called codons. An image shows an oblong circle. Running from one side of the circle to the other side are six small tubes. Each tube is divided into two different colors. Some are half green half red while the others are half blue half yellow. A bracket shows a group of three half tubes. Surrounding the circle are small clusters of spheres organized into the shapes of amino acids. One of the clusters is circled. TIM: Hundreds of thousands of codons in a row form a gene, the recipe for a full protein. An animation shows a column of the oblong circles connected. A square bracket connects the column to a cluster of spheres. TIM: Here's the thing, though: DNA is trapped inside the nucleus, never leaving. How does it get the recipe out to the rest of the cell, where proteins are made? The screen zooms out from inside the cell until the cell with organelles can be seen. TIM: How indeed, Moby? MOBY: Beep. TIM: Not a bad guess! DNA creates a sort of copy of the gene. The first step is transcription, which is just a fancy word for copying. An animation shows a double helix. The screen slowly zooms in on a column of oblong circles connected. TIM: A specially shaped molecule moves along the gene, "unzipping" the double helix. An animation shows two parallel, multicolored lines. A figure that resembles a rounded triangle is traveling along the lines. The rounded triangle is using a multicolored line segment to increase the distance between the two lines as it moves. TIM: That exposes the bases on each strand. Using one strand as a guide, the molecule assembles a copy of the opposing strand. The copied strand is RNA, or ribonucleic acid. The animation zooms into the rounded triangle. An oblong circle is shown. Running from one side of the circle to the other side are small tubes. The line segment the rounded triangle was using is connecting itself to one side of the tubes while destroying the other side. TIM: RNA is basically a half-DNA, with a single helix instead of a double. And rather than pairs, RNA has exposed bases, just waiting to stick to their opposites. The RNA version of a full gene is called messenger RNA, or mRNA. An image shows that now half tubes are connected to the line segment. The tubes are various colors. MOBY: Beep? TIM: Yep, because that's its job: telling the cell to build a specific protein. So mRNA leaves the nucleus and heads for a ribosome! This is the start of the translation stage: when the gene gets decoded into a protein. An animation shows the line segment travel from the nucleus of a cell outward to connect to a green figure resembling a thick star with rounded points. MOBY: Beep? TIM: Well, you remember all those amino acids floating around the cell? There's something I didn't tell you about them: each is attached to a short strand of RNA. Transfer RNA, or tRNA, is specially shaped to expose three bases at its tip. These are anti-codons: they match up with the codon for the amino acid they're attached to! An animation zooms into a cell. A small group of spheres connected by small tubes is shown. Running from one end of a sphere to the other is a squiggly line. Attached to the line are three half tubes. MOBY: Beep? TIM: The ribosome holds the mRNA in place to expose its leading codon. When the matching anti-codon comes along, they link up. The attached amino acid is left behind, and the mRNA advances. An animation shows the group traveling across the cell to a green figure resembling a thick star with rounded points. Sitting on the green figure is a line segment. Connected to the line segment are different colored half tubes. The group connects to the line segment. This process repeats. TIM: A new chunk of tRNA locks into place, and another amino acid is left behind. This repeats over and over, adding amino acids to the chain until the full protein is built! An animation shows a vertical, spiraling, cluster of red dots. At its center, a blue intertwining tube is shown. A wavy yellow tube is shown traveling from the blue tube. MOBY: Beep? TIM: Heh, it is pretty involved, and that's just to build a single protein! Now think about this: our cells are cranking out millions of proteins every second! Hence, this protein shake. A blender is heard. Slurping is heard. An animation shows Tim drinking a yellow mixture. TIM: Agh! Well, that's barfy. Category:BrainPOP Transcripts